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Osmoregulation in marine mammalsOsmoregulation in marine mammals has been investigated for over a century; however, a review of recent advances in our understanding of water and electrolyte balance and of renal function in marine mammals is warranted. The following topics are discussed: (i) kidney structure and urine concentrating ability, (ii) sources of water, (iii) the effects of feeding, fasting and diving, (iv) the renal responses to infusions of varying salinity and (v) hormonal regulation. The kidneys of pinnipeds and cetaceans are reniculate in structure, unlike those of terrestrial mammals (except bears), but this difference does not confer any greater concentrating ability. Pinnipeds, cetaceans, manatees and sea otters can concentrate their urine above the concentration of sea water, but only pinnipeds and otters have been shown to produce urine concentrations of Na+ and Cl- that are similar to those in sea water. This could afford them the capacity to drink sea water and not lose fresh water. However, with few exceptions, drinking is not a common behavior in pinnipeds and cetaceans. Water balance is maintained in these animals via metabolic and dietary water, while incidental ingestion and dietary salt may help maintain electrolyte homeostasis. Unlike most other aquatic mammals, sea otters commonly drink sea water and manatees frequently drink fresh water. Among the various taxonomic groups of marine mammals, the sensitivity of the renin-angiotensin-aldosterone system appears to be influenced by the availability of Na+. The antidiuretic role of vasopressin remains inconclusive in marine mammals, while the natriuretic function of atrial natriuretic peptide has yet to be examined. Ideas on the direction of future studies are presented.
Document ID
20040112378
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Ortiz, R. M.
(University of California Santa Cruz, CA 95064, United States)
Date Acquired
August 21, 2013
Publication Date
June 1, 2001
Publication Information
Publication: The Journal of experimental biology
Volume: 204
Issue: Pt 11
ISSN: 0022-0949
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: GM 58903-01
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
Review, Tutorial
NASA Discipline Cardiopulmonary
Review

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